﻿function ListNode(val,next){
    this.val =(val === undefined ? 0: val)
    this.next =(next === undefined ? 0 : next)
}

var deleteDuplicates = function (head){
    if(!head){
        return head;
    }
    
    let cur = head;
    while(cur.next ){
        if(cur.val === cur.next.val){
            cur.next = cur.next.next;
        }else{
            cur = cur.next;
        }
    }
    return head;
};